Conventionally, a fuse element is blown by self-heating when a rate-exceeding current flows therethrough and is used to interrupt the electrical current path. Examples of often-used fuse elements include, for example, fuses fixed by a holder wherein solder is enclosed in glass, chip fuses wherein an Ag electrode is printed onto a ceramic substrate surface, and screw-in or insertion type fuses wherein part of a copper electrode is made thinner and assembled into a plastic case.
Unfortunately, problems have been identified in the aforementioned existing fuse elements such as surface mounting using reflow being impossible and current ratings being low.
Moreover, a hypothetical reflow-use fuse device having high-speed blowout properties would, in general, preferably use a high melting point Pb(lead)-containing solder having a melting point of more than 300° C. in the fuse element so as not to be blown by reflow heat and in view of blowout properties. However, use of solder containing Pb is limited with few exceptions under the RoHS directive and demand for a transition to Pb-free products is expected to increase.
Therefore, there is demanded a fuse element capable of surface mounting by reflow, excellent in mountability to a fuse device, and applicable to large currents by increasing the rating.